1. Field of the Invention
The present invention relates to a camera module having a liquid lens, and more particularly, to an auto-focusing camera module having a liquid lens capable of automatically controlling focusing of the liquid lens.
2. Description of the Related Art
In general, personal communication services (PCS) such as mobile phones, PDA, portable PC have been increasingly used to transmit image data as well as character or voice data.
With these recent trends, a camera module is basically installed in the personal communication service (PCS) to facilitate the image data transmissions or video chats, etc.
FIG. 1 is a longitudinal cross-sectional view illustrating a conventional camera module. The camera module 1 includes a lens barrel 10 having a plurality of lenses 2 disposed in an inner space thereof; a male screw unit 11 formed in an outer surface of the body; and an incidence hole 13 formed through in an upper central region thereof.
The lens barrel 10 moves up and down in an optical axis direction relative to a housing 20 as a fixing member in rotation of the lens barrel 10 by engaging with the housing 20 having a female screw unit 21 formed in an inner surface thereof.
An image sensor 30 is disposed in a lower end of the housing 20, the image sensor 30 being provided with an image focusing region in which an image of a subject passed through the lens is focused, and the image sensor 30 is electrically connected to an upper or lower surface of a substrate 40.
Here, it is shown that the image sensor 30 is mounted in the upper surface of the substrate 40 by means of a plurality of wire members 35 using a wire bonding process, but the present invention is not particularly limited thereto. Also, the image sensor 30 may be mounted in the lower surface of the substrate using a flip-chip bonding process.
In FIG. 1, a reference numeral 15 represent a spacer for maintaining a distance between the lens 2 and an adjacent lens, a reference numeral 16 represent an iris for controlling light intensity through the incidence hole 13, a reference numeral 17 represents a press-fit ring for press-fitting the lens 2 into a lower end of the lens barrel 10 to fix the lens 2 in the lens barrel 10.
For the conventional camera module 1, the lens barrel 10 coupled to the housing 20 by screws should move in a forward direction or a reverse direction to control a focal distance between the image sensor 30 and the lens 2 provided in the lens barrel.
However, the camera module 1 has problems that it has a complicated structure in which the lens barrel and the housing are coupled by the screw, poor products are manufactured with a relatively higher level after its complete assembly, and an operation of adjusting a lens focus is carried out by hand in its assembly line, and therefore the manufacturing cost is high.
Also, it is problematic to manufacture a small product since there is one limit to reduce a height of the product due to a screw joint structure between the lens barrel and the housing.
Meanwhile, Japanese Patent Publication No. 2006-243572 (published on Sep. 14, 2006) discloses a camera module in which a liquid lens and a solid lens are disposed to adjust a lens focus
Here, the liquid lens has a configuration in which its cavity having a predetermined capacity is filled with a dielectric fluid, its upper portion is filled with an electrolyte solution, and electrodes are formed in a lower portion of the dielectric fluid. In this configuration, when an electric current flows in the electrodes and the electrolyte solution, the substances that are in contact with the liquids may be soaked with the liquids due to the change in surface tension of the liquids (so-called, an electro-wetting phenomenon). Therefore, the electro-wetting phenomenon results in the change in an interfacial angle, for example a contact angle, of the dielectric electrolyte fluid.
As described above, the liquid lens is used to easily control its focus without its mechanical driving using the electro-wetting phenomenon since a curvature of the interface is changed by the equilibrium wetting condition in the interface.
However, in order to apply an electric current to the liquid lens in the conventional camera module, a flexible printed circuit (FPC) that is electrically coupled to the electrodes and the electrolyte solution is positioned and fixed by the filler with which the upper portion of the lens barrel is filled, and then drawn out. Then, an input of the FPC should be electrically coupled to a power supply unit (not shown).
In this case, it is very cumbersome to dispose and fix the FPC in the lens barrel using the filler with which the upper portion of the lens barrel is filled, and the exposed FPC may be short or damaged by the interference with the other members in mounting the assembled camera module in a main substrate.
Also, it was difficult to simplify an assembly structure of the liquid lens and reduce the manufacturing cost since the liquid lens into which the FPC is assembled should be assembled into the camera module.